On Thanksgiving, we collectively loosened our belt and enjoyed second helpings. The problem is that all too many Americans opt for extra servings the other 364 days of the year as well. The result is an obesity crisis consuming 10 cents of every health dollar and resulting in an explosion of diabetes in our inner cities. With rising rates of obesity, many local and state governments have looked to the idea of a soda tax. Heavily taxing sweetened beverages has won praise from the governor of New York and the president, and earlier this month, the presidents debt commission recommended it. The soda tax and similar initiatives may make us feel good about tackling obesity, but they are unlikely to better our health.

Many insist that soda taxes are needed to curb obesity v a solution that conveniently pours more revenue into government coffers. The double standards are evident: Wheres the latte tax? No honest policymaker can call for a soda tax without a plan to tax flavored coffees, too. A 12-ounce “low-fat” Caramel Macchiato has more calories than a 12-ounce serving of Coca-Cola. Why tax one and not the other?

I mention lattes because Washington state is the home of Starbucks, the company that got us hooked on high-end coffee. And on Election Day, more than 60 percent of Washington state voters passed Initiative I-1107, voting to overturn its soda tax (and the candy-bar and bottled-water taxes). Opposition crossed urban and rural boundaries: Just two counties produced majority votes to uphold the taxes. Liberal latte-drenched King County (Seattle-Tacoma) supported keeping the taxes by a margin of just 6 percent.

Farther south in San Francisco, city council members passed a “Happy Meal ban,” imposing nutritional standards on any meal sold with a bundled toy. Outgoing San Francisco Mayor Gavin Newsom - no slouch on the issue of child obesity  vetoed the ban, arguing that it was the wrong approach. “Parents, not politicians,” he observed, “should decide what their children eat.”

Strangely, San Franciscos council hasnt mustered the same level of outrage against family restaurants where “kids under 6 eat free,” no matter how unhealthy the menu options. Handing out plates of free food is as big an incentive for obesity as any toy ever will be. Why attack one kind of overindulgence and not the other?

On the East Coast, New York City is struggling to keep its budget under control. Still, Mayor Michael R. Bloomberg spent much political capital in the past two years developing new health guidelines for New Yorks restaurants. Mr. Bloomberg had hoped new standards could somehow lead the nation to embrace better dietary habits, with calorie counts and lower salt intake. Mr. Bloombergs intentions are good. More health information is reasonable, and many American food products really do have unhealthy levels of salt. But redefining Americas diet from one citys council chamber isnt so simple. Millions of consumers equate “more calories” with “more value.” So its not surprising that some studies  like one study led by the New York University School of Medicine  found that adding calorie counts to menus marginally increasedconsumption in poor neighborhoods where obesity rates are highest.

Likewise, New Yorks effort to influence salt intake can be confounded by the ultimate dietary loophole: the salt shaker. Americans must embrace the virtues of moderating salt intake themselves first. Otherwise, theyll just respond to lower salt levels in prepared foods by shaking out heart-stopping quantities of the stuff themselves. Ten percent to 20 percent of the typical Americans sodium intake is added after the food is served.

As a physician, I must be blunt: Obesity and preventable diseases are killing us. As a public-policy analyst, I must be equally blunt: Obesity is a threat to the American budget, the American health insurance subscriber, the American employer and the American military recruiter. The obesity epidemic can only be curbed with strong leadership. But micromanagement of the American diet from elective office is not going to accomplish anything other than grandstanding. If you thought banning liquor in America in the 1920s was a failure, try banning eggs Benedict or taxing tostadas and see how far you get.

We wont conquer obesity if we see the American diet as nothing more than a menu of opportunities for inconsistent taxes and impractical “wishful thinking” regulations. That would be like, well, turkeys voting for Thanksgiving.